Transmission system



Dec. 24, 1935, H M BASCQM ET Alm l 29025945 TRANSMISSION SYSTEM Filed oet.y 4, 1929 s sheets-sheet 1 MLM/Ama Dec. 24, 1935.- H, M, BASTCOM Er AL 25,025,145

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Patented Dec. 24, 1935 UNITED STATES PATENT OFFICE 2,025,145 TRANSMISSION SYSTEM Application October 4, 1929, Serial No. 397,311

9 Claims.

This invention relates to transmission systems and particularly to the automatic selection and insertion of speech repeating and line balancing devices between the lines of automatically completed telephone connections.

The object of this invention is to improve and simplify the establishing of automatic telephone connections requiring such devices in the transmission circuits.

io Heretofore telephone repeaters have been automatically selected and inserted between two telephone lines in response to the manual connection of two lines or simultaneously with the automatic connection of two lines. In the case of systems where the connections are established manually a network is provided for each line suitable for the balancing of the corresponding line. This network is usually automatically selected simultaneously with the selection of a repeater and connected thereto to balance the connected line. In the case of systems where the connections are established automatically, compromise networks are permanently connected in the repeater to balance the connected lines although the balancing characteristics'of these networks will not be ideal for lines connected together having varying electrical transmission characteristics.

A feature of this invention is a System of the above type in which networks for accurately balancing the individual lines are automatically selected simultaneously with and in response to the automatic selection and connection of the repeater between the calling line and the called line.

Another feature is a system of this kind in which the Selection of the network for the calling line is accomplished through means controlled by electrical conditions individual to the calling line and in which the selection of the network for the called line is accomplished through means controlled by impulses received over the calling line for the selection of the called line.

This invention has been illustrated in the accompanying drawings in which Fig. l shows the 4o invention applied to an arrangement whereby balancing networks may be selected for two trunk lines connected through a repeater; Fig, 2 shows a similar system with a modied arrangement for Selecting the balancing networks; while Fig.

3 shows the invention applied to a system in which balancing networks are only selected for insertion at the incoming end of a repeater for balancing the characteristics of an incoming trunk which may be connected to an outgoing trunk to which the repeater is permanently connected.

Referring now to the preferred form of the invention as illustrated in Fig. 1, the incoming end of a trunk A has been shown having access to a repeater equipment B through a first selector C. A Second selector D and a third Selector 5 E have been shown for connecting the incoming trunk to an outgoing trunk F through the repeater B, or for connecting these trunks directly without the repeater B as desired. Equipment for selecting balancing networks for these trunks 1o has also been shown including switches G, I-I and I.

It should be understood that the above mentioned switches C, D, E, H and I may be of any well known step-by-step types responsive to dial I impulses, and switch G may be of the well known 15 step-by-step type having no normal position and operative to preselect an idle equipment includving switches such as H and I.

If a connection is desired with a repeater inserted between the trunks A and F, the operation 2o of the system is as follows: When a call is incoming over trunk A line relay 5 operates from battery and ground, through the windings of this relay, through the upper armatures and back contacts of the cut-off relay 6 and tip and ring 25 conductors of the trunk A, through a loop closed between these conductors o1 trunk A at a distant office. Relay 5 in operating closes a connection at its upper armature and front contact to ground for a start wire 1 which connects the trunk 30 A through a line iinder, not shown, to an idle first selector C in any manner well known in the art. The operator or subscriber at the distant end of trunk A will now dial the first digit of the number of the desired outgoing trunk group 35 and thereby cause the selector C to advance its brushes to connect with a set of terminals through which a repeater may be inserted between the trunks. The arrangement of the terminal banks in the selector may be such that, for example, the 40 terminals in the uppermost level may be assigned to connections in which repeaters are included. When the connection to a set'of terminals through which a repeater may be inserted, has been established by selector C, a circuit is completed through 45 the tip and ring conductors of trunk A for the operation of relay 8. This circuit extends through the middle right hand and outer left hand armatures of relay I0 and middle left hand and outer right hand armatures of relay Il to the tip 5o and ring conductors and the usual pulsing relay in selector D. Relay 8 in operating closes a circuit for the operation of relays l0 and Il from battery through the windings of these relays, armature and back contact of relay l2, lower armature and'front contact of relay 8 to ground.

Relay I 0 in operating removes the short circuit for the left hand windings of transformer I4 and relay II in operating removes the short circuit for the right hand windings of transformer I5 and the windings of retardation coil 2I so that the connection to the selector D will now extend through their windings. At the time relay 8 operates ground is also connected through the sleeve circuit of the selector D for the operation of vrelay I6. This ground connection eX- tends to battery through the windingof relay I6. It also extends through the selector C to control the line nder and cut-oir relay IiV through the usual circuit arrangement of this type. It'should be understood that it is well known in the art that this ground connection has alreadyV caused the operation of the cut-off relay 6 over a circuit from battery, winding of relay 6, lower armature and front contact of line relay 5 to said ground. Relay 6 when operated opened the connection for thevline relay 5 to cause it to release while relay 6 established a locking circuit for itself from battery to ground through its winding and lower contact. Relay I6 in operating prepares a portion of a circuit at its armature and front contact for the subsequent operation of relay I2 and also serves to close a circuit to ground through its right hand armature and front contact for the purpose of lighting the laments of the vacuum tubes used in the usual voice frequency repeaters indicated by boxes I9 and 20 respectively. The details of these voice frequency repeaters have not been shown as their construction is Well known in the art. Y

The operator or'subscriber connected at the distant end of trunk A will'now dial the second digit of the desired number. Relay 8 will therefore respond to the dial pulses of this digit and on the first release of relay 8, relay I2 is operated Vover a circuit from battery.,` winding of relay I2, Yleft hand armature and front contact of relay I6 to ground at the' lower armature and back contact of relay 8. Relay I2 is slow to release so that it will remain operated during the succeeding pulsing operations of relay 8. On this first release of relay 8, relays I8 and II are released and Vwill not operate again during the sending of the second digit due to the opening of the circuits Y therefor at the armature and back contact of" `relay I2.

The release of relays I0 and II reestablishes the short circuit for the left hand windings of'transformer I4, the right hand windingsv of transformer I5 and retardation coil 2I Vto provide a better pulsing circuit; the input cir- Y cuits to the voice repeater are also opened to prevent so-called singing of the repeater during the pulsing. It shouldbe noted that the retardation coil 2I is in series with the tip and ring conductor during the talking condition, to pro- Vvide a high impedance in the return path provided through'the signaling by-pass circuit, to prevent repeater singing. After the pulses of the second digit have been completed and the second selector D thereby controlled to extend the connection to the third selector E, relay I2 is released and thereby causes the reoperation of relays IllV and II to reestablish the circuit through transformer I4, retardation coil`2I and transformer I5.

'Y The third digit is now sent and during the sending of this digit'relays 8 and I2 and I Dand I I are operated in the same manner, while the third selector E is controlled to extend the connection -to trunk F. The talking circuit is then established 2,025,145 o between trunks A and F for talking conditions through the windings of the transformers I4 and I5, the condensers 22, 23, 24 and 25 and the voice frequency repeaters I9 and 28; at the same time the signaling circuit, which presents a high impedance to voice frequency currents, is established through the left handwindings of transformer I4, relay 8, retardation coil 2| and the right hand windings of transformer I5.

It should, however, be observed that in order to establish proper transmission characteristics for trunks A and F, balancing networks must be inserted in this connection. The insertion of the balancing network for trunk A is accomplished as follows: Trunk A and others may be connected at the conductor26 and corresponding conductors in diiferent manners depending on the particular type of balancing network required in each case. Conductor 25 may be open or connected as shown directly to ground or through a resistance to ground. vIf trunk A has its conductor 28 open it will be noted, that relays 21 and 28 will remain in a non-operated condition as there is no ground connection for the circuit from battery through the winding of these relays the fourth terminal and brush of selector C, lower outer armature and front contact of relay 6 to conductor 26. Hence a balancing network indicated by means of a box at 30 will remain connected to the transformer I4 as follows: From this network through the upper armatures and back contacts of relay 32, lower armatures and back contacts of relay 33, to the upper right hand winding of transformer I4 through the right hand outer armature and front contact of relay I8 and to the lower winding of transformer I4 directly.

connected through a. resistance to ground, only Y relay 21 would haveoperated as relay 28 is of such marginal characteristics as not to operate when this resistance is inserted in the circuit. In this case the operation of relay 21 would have closed a circuit for the operation of relay 33 and the balancing network 36 would have been connected to the transformer I4 through the lower armatures and front contacts of relay 33. In this manner the various trunks incoming from distant oflices may be divided into groups having the same or similar transmission characteristics, one group requiring, for example, a balancing network such as 3D, another group a balancing network such as 35', and a third group a balancing network such as 36. It is obvious that other arrangements of this circuit may be made to provide other groups of incoming trunks with suitable balancing networks. For example, other different electrical characteristics may be established for the circuit through conductor 23 to operate variousv other arrangements of Vrelays to connect different balancing networks for corresponding groups of trunks.

Trunks such as F leading to distant ofiices may also require different types of balancing networks. To this end a circuit arrangement as follows has been provided. On the operation of relay I6 at the seizure of the repeater B, the circuit from ground at the selector D is also extended to the conductor 31 through the make-before-break contacts of relay 38 to switch G. This switch will have previously selected an idle selector H and the application of ground on conductor 31 will make selector H busy to other switches similar to G. Switch G may be of the usual step-by-step rotary line switch type which is often employed in selecting idle common equipments for various purposes in automatic telephone systems as is well known in the art. If it is assumed that switch G had selected the selector H, this selector will-be actuated when relay 8 responds to the impulses of the second digit as a pulsing circuit is closed through the upper armature and front contact of relay 8 for the actuation of the usual pulsing relay in selector H o-ver the conductors 46 and 4I that extend through the lower and upper inner armatures and back contacts of relay 38, the windings of polar relay 42, brushes 44 and 43 of switch G, through the pulsing relay (not shown) of selector H to battery and ground. Selector H will thereby be actuated to advance to a position in a level corresponding to that selected by selector D when responding to the impulses of the second digit. Similarly when the third digit causes the relay 8 to respond to the impulses thereof, the succeeding selector I is actuated to take a position in a level corresponding to that selected by selector E when actuated by the impulses of the third digit. Selectors H and I will consequently select a point which corresponds to trunk F and when this is accomplished a circuit is completed through the tip and ring conductors of selectors H and I, make-beforebreak contacts of relay 41, windings of relay 48, to battery and ground. Relay 48 is now operated to `close at its lower armature and front contact a circuit to ground, back through selectors I and H to hold them operated as is well known in the art. An obvious circuit is also completed by the operation of relay 48 for the operation of relay 50. This relay is slow in operating. Relay 48 in operating provides a third circuit through its upper outer armature and front contact for the conductor 53 which extends back through the selectors I, H and switch G through the upper outer armature and back contact of relay 38, windings of relays 55 and 56 in series to battery. Depending now on the point selected by selectors H and yI an electrical condition will be established on the conductor 53 for the selection of the proper balancing network for trunk F.

If the conductor 53 is connected through a resistance to ground only relay 55 will operate in this circuit as relay 56 is marginal and thus close the circuit for the operation of relay 51. This relay in operating will connect a balancing network as indicated by box 59 through its armatures and front contacts, the left hand upper winding of transformer I over the connection through the left hand outer armature and front contact. of relay II for one conductor and directly to the lower left hand winding of transformer I5 for the other conductor.

If the conductor 53 had been connected directly to ground relays 55 and 56 would have operated to close a circuit for the operation of relay 63. This relay would then have connected the balancing network indicated by box 65 through the lower armatures and front contacts of relay 63 to the transformer I5.

If another point had been selected, the conductor 53 would have been open as shown and in this case on the establishing of the connection through the relay 58 to battery and ground, a connection would merely have been established through the armature and front contact of this relay to ground for holding the switches I and H operated. In this case as the conductor 53 is opened, neither relay 55 nor relay 56 would have operated and consequently a balancing network such as indicated by box 61 would have been connected through the upper armatures and back contacts of relay 63 and the lower armatures and back contacts of relay 51 to the transformer I5.

It should be noted that when either relay 55 or relay 56 is operated, or both of these relays are operated, they are locked in operated positions through their lower armatures and lower contacts to the ground connection established through the sleeve of selector D. It is therefore evident that the common equipment for selecting the balancing networks for the outgoing trunk are not required after they have been operated. The selectors H and I may therefore be released as soon as the identifying condition has been established. It should be noted in the case of the connection through relay 48 that when relay 50 is operated an obvious circuit is completed for the operation of relay 41. This relay in operating reverses the connection from battery and ground through the windings of relay 48, back through the tip and ring conductors of the selectors I and H and switch G and when this takes place relay 42 which is polarized operates to close an obvious circuit for the operation of relay 38. This relay operating opens the ground connections from lead 31 to the switch G and selectors H and I so that these switches are released., Relay 38 in operating establishes a locking circuit for itself from battery, the lower outer armature and front contact to ground and lead 31 so that this relay is now maintained operated as long as the connection remains in use. The arrangement with relay 58 is provided for the class of trunks where the network 61 is to be used, and where it is not necessary, therefore, to transmit any signal over lead 53 or to operate either of relays 55 or 56. Therefore, as soon as the connection is established to relay 58 it operates and as the connection from battery and ground is permanently reversed, relay 42 is operated immediately to release the common equipment through the operation of relay 38.

As mentioned above, a talking circuit through the repeater is now completed and the proper balancing networks selected for trunks A and F,

respectively, so that talking over this connection may now begin. When the connection is to be released, the holding loop over the tip and ring conductor is opened, releasing relay 8, which in turn releases relays I0 and II, and after an interval the ground is removed from the sleeve conductor at the outgoing trunk F and relays I6 and 38 are released and also such relays as were operated during the selection of the balancing network, namely 21, 28, 33, 32, 55, 55, 63 and 51, so that the circuit arrangement of the repeater B is returned to normal condition.

Referring now to Fig. 2 in which the invention has been applied to a modified circuit arrangement for connecting the two trunks A and F through the repeater B. In this case the arrangement may be such that selectors such as C will have associated with them balancing networks suitable for balancing the incoming trunks. These balancing networks may be connected through the brushes and terminals of the selectors; to the. transformers. of' the; repeatersv selected.

Ilheoperationsof the circuitsinthis figure for establishing aconnection through a repeater are :55. identical with the operations of the circuit shown in Fig. l, except for theA means for associating the balancing networksv with ,the trunks` and F. 'I'he same numerals andv identifying letters haveY been applied to the corresponding elements The connectionv through the sleeve circuit from selector D for'the operation of relay i6 is also extended toconductorI 15 for control of selectors J and K, which are similar to selectors H and I, except that five wipers and banks are provided When relay 3` responds to the pulsesv Voi the second digit, selector J is operated through D and- E respectively, to select the point corre- '.works of the proper characteristics.

sponding to trunk F. The points selectable by selector K may beassociated with balancing net- For example, if selector K connects with the set-of terminals shown at Tl the balancing network indicated by'box .18A will be associated with the transformer I5. If the set of terminals had been seiected, the'balancing network indicated by'box 8i would have been connected and similarly other points may be selected toV connect other balancing. networks to the transformer l5 for properly' balancing the corresponding outgoing trunk confnected at vthe selector E.

When the connection between trunks A and F is released, the selectors J and K are released on removal of the ground on the sleeve at outgoing trunk F, through E and D. It will thus be seen thatin this case the selectors J and K remain operated and the connection from the balancing network to transformer I5 is kept established as long as the connection remains. Y

Referring now to Fig. 3, the invention has been applied to a circuit arrangement in whichV an incoming trunk L may be associated with a trunk M. In this case a proper balancing networki may be selected for trunk L whereas the trunk M has a balancing network 82 permanently connected through the transformer 83 of the repeater N.

Calls incoming over trunks such as L may be ex- Y tended over line nderssuch as O to trunks such as M; It should be understood that dirierent groups of incoming. trunks may terminate in such line findersy and. have access Vto a number of outgoing trunks, each one of which is associated permanentlyA with a repeater and a proper balancing;

When a call is incoming over trunk L line re.-V

lay 85 is operated over the tip and. ring conductors and this relay establishesthe starting circuit .through conductor 86 tov start a line iinder such as O to lind the trunk L in a manner Well known in the art. When the connection is establishedto the trunk M, dialing over trunk L may take place in a manner similar to that shown in Fig. 1 and passed by the repeater N to trunk M. No details of these pulse repeating and control circuits have been shown inV this case, as receiving dial pulses from the incoming trunk on a loop signaling basis and repeating them on Ya composite signaling basis on the outgoing trunk is a circuit arrangement well known in the art..

Depending now onl the electrical cl'laracteris-l tics'of the conductor 88 the proper balancing network" will be associated with the transformer SillA of repeater N to balance against the trunk L. Ii' conductor 88 Vis open, neither relay 92 nor relay 93 vwould be operated and the balancing 5 network indicated by box 95 will be connected through the upper armaturesv and back contacts of relays 96l and 91 to the transformer 9D.

It conductor 801 is connected directly to ground, relays 92` and 93 will operate and close the cir- 10y cuit for the operation of relay 96 and the balancing network indicated by box 99 will be connected to the. transformer 90, whereas ifV conductor 88Y is connected through a resistance to groundv only relay 92 will operate as relay 93 is 15 marginal and thus cause the operation of relay S7 to connect the balancing network indicatedby box |00'r to the transformer 90'.

While the invention has only been applied to three different-types of systems it is obvious that 20A it may readily bel applied to a plurality of other systems without departing from the spirit thereof.

What is claimed."- is;

1. In a telephone system, incoming lines of 25 different transmission characteristics, an outgoing line, a switch, a voice frequency repeater havingV its outgoing side connected to the outgoing line and. its incoming side connected with said switch, line compensating networks individual to 302 said repeater' and suitable for use with the incoming side ci said repeater, a line compensating network connectedvin the outgoing side of said repeater, means responsive t0 the seizure of an incoming line for actuating said switch to 35531V connect said incoming line with the incoming side of said repeater and means including marginally responsive relays actuated in response to sa"d connection for associating a Vcorresponding one of said first mentioned line compensating 40- networks with the incoming side of said repeater.

2. In a telephone system, lines, repeaters, balancing networks common to said repeaters, andautomatic means for connecting two linesv through a repeater and for selecting lbalancing networks 45 for said lines, said means including switches controlled by directive impulses over one ofv said lines.

3. In a telephone system, a calling line, a called line, repeaters, networks, and means including 50 switches responsive to current impulses incoming over the calling line ior selecting a repeater, se lecting the called line, selecting a network for`l balancing Vsaid called'line and connecting said repeater between said lines. 55

4; In a telephone system, incoming lines, outgoing lines, repeaters, means responsive to directive impulses incoming over an incoming line for connecting said incoming line'to an outgoing line through a repeater, balancing networks, means 60 ing side of a repeater, switching means asso- 70` ciated with the outgoing side of the repeater for selecting outgoing lines, a separate group of balancing networks indivi-dual to eachrepeater, means responsive to the' selection of a repeater by all' l'flCOmng line for connecting to saidv re- 75 peater a suitable network from the associated group for balancingv said incoming line, and means responsive to the selection of an outgoing line through a repeater for connecting to said repeater a suitable network from the associated group for balancing said outgoing line.

6. In a telephone system, incoming lines, outgoing lines, repeaters, switching means associated with the incoming lines for selectin-g the incoming side of a repeater, switching means associated with the outgoing sides of the repeaters for selecting outgoing lines, a separate group of balancing networks for each repeater, means responsive to the selection of a repeater by an incoming line for connecting a suitable network to said repeater from the associated group for balancing said line, and auxiliary switching means responsive to the selection of an outgoing line through a repeater for selecting and connecting tc said repeater a suitable network from the associated group for balancing said outgoing line.

7. In a telephone system, incoming lines, outgoing lines, repeaters, means for connecting the incoming line with an. outgoing line either directly or through a repeater, a balancing network associated with each incoming line, a group of balancing networks for outgoing lines associated with said rep-eaters, means responsive to the connection of an incoming line to an outgoing line through a `repeater for connecting the network individual to said incoming line through said repeater for the balancing of the incoming line and for selecting and connecting a suitable network of the group associated with said repeaters to said interpolated repeater for balancing said outgoing line.

8. In a telephone system, incoming lines of d i'erent characteristics, means individual to each of said incoming lines for indicating the character of each incoming line, outgoing lines of different characteristics, repeaters, means re- 5 sponsive to directive impulses incoming over an incoming line for connecting said incoming line to an outgoing line through a repeater, balancing networks, means controlled by the character indicating means individual to said incoming line 10 and responsive to the interconnection of said incoming and outgoing lines for associating with said repeater a network suitable for balancing said incoming line, and means responsive to said impulses lfor associating a network with said in- 15 terpolated repeater suitable for balancing said outgoing line.

9. In a telephone system, incoming lines of different characteristics, means individual to each of said lines for indicating the character of 2o said line, outgoing lines of different characteristics, a repeater, switching means controlled by directive impulses incoming over one of said incoming lines for connecting said incoming line through said repeater to a desired one of said 25 outgoing lines, line balancing networks of different characteristics for use in balancing interconnected lines, marginal relay 'means controlled by the character indicating means of said incoming line for selecting a suitable one of said networks 30 for balancing said incoming line, and switching means controlled by said impulses for selecting a suitable one of said networks for balancing said outgoing line.

HENRY M. BASCOM. OTTO A. FRIEND. MARCELLUS B. McDAVITT. 

